1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Margo Seltzer. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11 #if defined(LIBC_SCCS) && !defined(lint) 12 static char sccsid[] = "@(#)hash_buf.c 5.9 (Berkeley) 09/08/91"; 13 #endif /* LIBC_SCCS and not lint */ 14 15 /* 16 * PACKAGE: hash 17 * 18 * DESCRIPTION: 19 * Contains buffer management 20 * 21 * ROUTINES: 22 * External 23 * __buf_init 24 * __get_buf 25 * __buf_free 26 * __reclaim_buf 27 * Internal 28 * newbuf 29 */ 30 31 #include <sys/param.h> 32 #include <db.h> 33 #include <errno.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #ifdef DEBUG 37 #include <assert.h> 38 #endif 39 #include "hash.h" 40 #include "page.h" 41 #include "extern.h" 42 43 static BUFHEAD *newbuf __P((u_int, BUFHEAD *)); 44 45 /* Unlink B from its place in the lru */ 46 #define BUF_REMOVE(B) { \ 47 (B)->prev->next = (B)->next; \ 48 (B)->next->prev = (B)->prev; \ 49 } 50 51 /* Insert B after P */ 52 #define BUF_INSERT(B, P) { \ 53 (B)->next = (P)->next; \ 54 (B)->prev = (P); \ 55 (P)->next = (B); \ 56 (B)->next->prev = (B); \ 57 } 58 59 #define MRU hashp->bufhead.next 60 #define LRU hashp->bufhead.prev 61 62 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 63 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 64 65 /* 66 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 67 * address is a bucket index. If prev_bp is not NULL, then it points to the 68 * page previous to an overflow page that we are trying to find. 69 * 70 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 71 * be valid. Therefore, you must always verify that its address matches the 72 * address you are seeking. 73 */ 74 extern BUFHEAD * 75 __get_buf(addr, prev_bp, newpage) 76 u_int addr; 77 BUFHEAD *prev_bp; 78 int newpage; /* If prev_bp set, indicates a new overflow page. */ 79 { 80 register BUFHEAD *bp; 81 register u_int is_disk_mask; 82 register int is_disk, segment_ndx; 83 SEGMENT segp; 84 85 is_disk = 0; 86 is_disk_mask = 0; 87 if (prev_bp) { 88 bp = prev_bp->ovfl; 89 if (!bp || (bp->addr != addr)) 90 bp = NULL; 91 if (!newpage) 92 is_disk = BUF_DISK; 93 } else { 94 /* Grab buffer out of directory */ 95 segment_ndx = addr & (hashp->SGSIZE - 1); 96 97 /* valid segment ensured by __call_hash() */ 98 segp = hashp->dir[addr >> hashp->SSHIFT]; 99 #ifdef DEBUG 100 assert(segp != NULL); 101 #endif 102 bp = PTROF(segp[segment_ndx]); 103 is_disk_mask = ISDISK(segp[segment_ndx]); 104 is_disk = is_disk_mask || !hashp->new_file; 105 } 106 107 if (!bp) { 108 bp = newbuf(addr, prev_bp); 109 if (!bp || __get_page(bp->page, addr, !prev_bp, is_disk, 0)) 110 return (NULL); 111 if (!prev_bp) 112 segp[segment_ndx] = 113 (BUFHEAD *)((u_int)bp | is_disk_mask); 114 } else { 115 BUF_REMOVE(bp); 116 MRU_INSERT(bp); 117 } 118 return (bp); 119 } 120 121 /* 122 * We need a buffer for this page. Either allocate one, or evict a resident 123 * one (if we have as many buffers as we're allowed) and put this one in. 124 * 125 * If newbuf finds an error (returning NULL), it also sets errno. 126 */ 127 static BUFHEAD * 128 newbuf(addr, prev_bp) 129 u_int addr; 130 BUFHEAD *prev_bp; 131 { 132 register BUFHEAD *bp; /* The buffer we're going to use */ 133 register BUFHEAD *xbp; /* Temp pointer */ 134 register BUFHEAD *next_xbp; 135 SEGMENT segp; 136 int segment_ndx; 137 u_short oaddr, *shortp; 138 139 oaddr = 0; 140 bp = LRU; 141 /* 142 * If LRU buffer is pinned, the buffer pool is too small. We need to 143 * allocate more buffers. 144 */ 145 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 146 /* Allocate a new one */ 147 bp = malloc(sizeof(struct _bufhead)); 148 if (!bp || !(bp->page = malloc(hashp->BSIZE))) 149 return (NULL); 150 hashp->nbufs--; 151 } else { 152 /* Kick someone out */ 153 BUF_REMOVE(bp); 154 /* 155 * If this is an overflow page with addr 0, it's already been 156 * flushed back in an overflow chain and initialized. 157 */ 158 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 159 /* 160 * Set oaddr before __put_page so that you get it 161 * before bytes are swapped. 162 */ 163 shortp = (u_short *)bp->page; 164 if (shortp[0]) 165 oaddr = shortp[shortp[0] - 1]; 166 if ((bp->flags & BUF_MOD) && __put_page(bp->page, 167 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 168 return (NULL); 169 /* 170 * Update the pointer to this page (i.e. invalidate it). 171 * 172 * If this is a new file (i.e. we created it at open 173 * time), make sure that we mark pages which have been 174 * written to disk so we retrieve them from disk later, 175 * rather than allocating new pages. 176 */ 177 if (IS_BUCKET(bp->flags)) { 178 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 179 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 180 #ifdef DEBUG 181 assert(segp != NULL); 182 #endif 183 184 if (hashp->new_file && 185 ((bp->flags & BUF_MOD) || 186 ISDISK(segp[segment_ndx]))) 187 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 188 else 189 segp[segment_ndx] = NULL; 190 } 191 /* 192 * Since overflow pages can only be access by means of 193 * their bucket, free overflow pages associated with 194 * this bucket. 195 */ 196 for (xbp = bp; xbp->ovfl;) { 197 next_xbp = xbp->ovfl; 198 xbp->ovfl = 0; 199 xbp = next_xbp; 200 201 /* Check that ovfl pointer is up date. */ 202 if (IS_BUCKET(xbp->flags) || 203 (oaddr != xbp->addr)) 204 break; 205 206 shortp = (u_short *)xbp->page; 207 if (shortp[0]) 208 /* set before __put_page */ 209 oaddr = shortp[shortp[0] - 1]; 210 if ((xbp->flags & BUF_MOD) && 211 __put_page(xbp->page, xbp->addr, 0, 0)) 212 return (NULL); 213 xbp->addr = 0; 214 xbp->flags = 0; 215 BUF_REMOVE(xbp); 216 LRU_INSERT(xbp); 217 } 218 } 219 } 220 221 /* Now assign this buffer */ 222 bp->addr = addr; 223 #ifdef DEBUG1 224 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 225 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 226 #endif 227 bp->ovfl = NULL; 228 if (prev_bp) { 229 /* 230 * If prev_bp is set, this is an overflow page, hook it in to 231 * the buffer overflow links. 232 */ 233 #ifdef DEBUG1 234 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 235 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 236 (bp ? bp->addr : 0)); 237 #endif 238 prev_bp->ovfl = bp; 239 bp->flags = 0; 240 } else 241 bp->flags = BUF_BUCKET; 242 MRU_INSERT(bp); 243 return (bp); 244 } 245 246 extern void 247 __buf_init(nbytes) 248 int nbytes; 249 { 250 BUFHEAD *bfp; 251 int npages; 252 253 bfp = &(hashp->bufhead); 254 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 255 npages = MAX(npages, MIN_BUFFERS); 256 257 hashp->nbufs = npages; 258 bfp->next = bfp; 259 bfp->prev = bfp; 260 /* 261 * This space is calloc'd so these are already null. 262 * 263 * bfp->ovfl = NULL; 264 * bfp->flags = 0; 265 * bfp->page = NULL; 266 * bfp->addr = 0; 267 */ 268 } 269 270 extern int 271 __buf_free(do_free, to_disk) 272 int do_free, to_disk; 273 { 274 BUFHEAD *bp; 275 276 /* Need to make sure that buffer manager has been initialized */ 277 if (!LRU) 278 return (0); 279 for (bp = LRU; bp != &hashp->bufhead;) { 280 /* Check that the buffer is valid */ 281 if (bp->addr || IS_BUCKET(bp->flags)) { 282 if (to_disk && (bp->flags & BUF_MOD) && 283 __put_page(bp->page, 284 bp->addr, IS_BUCKET(bp->flags), 0)) 285 return (-1); 286 } 287 /* Check if we are freeing stuff */ 288 if (do_free) { 289 if (bp->page) 290 free(bp->page); 291 BUF_REMOVE(bp); 292 free(bp); 293 bp = LRU; 294 } else 295 bp = bp->prev; 296 } 297 return (0); 298 } 299 300 extern void 301 __reclaim_buf(bp) 302 BUFHEAD *bp; 303 { 304 bp->ovfl = 0; 305 bp->addr = 0; 306 bp->flags = 0; 307 BUF_REMOVE(bp); 308 LRU_INSERT(bp); 309 } 310